Genetics
Work of Gregor Mendel
• Genetics is the scientific study of heredity.
• Gregor Mendel was an Austrian monk. His
work was important to the understanding of
heredity.
• Mendel carried out his work
with ordinary garden peas.
Work of Gregor Mendel
• Mendel knew that
– the male part of
each flower
produces pollen,
(containing sperm).
– the female part of
the flower produces
egg cells.
Work of Gregor Mendel
• During sexual reproduction, sperm and egg
cells join in a process called fertilization.
• Fertilization produces a new cell.
• Pea flowers are self-pollinating.
Work of Gregor Mendel
• Mendel had true-breeding pea plants that, if
allowed to self-pollinate, would produce
offspring identical to themselves.
Cross-pollination
Mendel was able to
produce seeds that had
two different parents.
Work of Gregor Mendel
• Genes and Dominance
– A trait is a specific characteristic that varies from
one individual to another.
• Mendel studied seven pea plant traits, each
with two contrasting characters.
• He crossed plants with each of the seven
contrasting characters and studied their
offspring.
• Each original pair of
plants is the P (parental)
generation.
• The offspring are called
the F1, or “first filial,”
generation.
• The offspring of crosses
between parents with
different traits are
called hybrids.
Mendel’s F1 Crosses on Pea Plants
Work of Gregor Mendel
• Mendel's first conclusion
– biological inheritance is determined by factors
that are passed from one generation to the next
• Today, scientists call the factors that
determine traits genes.
Work of Gregor Mendel
• Each of the traits Mendel studied was controlled
by one gene that occurred in two contrasting
forms that produced different characters for each
trait.
– The different forms of a gene are called alleles.
• Mendel’s second conclusion
– principle of dominance
– some alleles are dominant and others are recessive
Work of Gregor Mendel
• Segregation
– Mendel crossed the F1
generation with itself to
produce the F2 (second
filial) generation.
– The traits controlled by
recessive alleles reappeared
in one fourth of the F2
plants.
Work of Gregor Mendel
• The reappearance of the trait controlled by
the recessive allele indicated that at some
point the allele for shortness had been
separated, or segregated, from the allele for
tallness.
Work of Gregor Mendel
• Mendel suggested
that the alleles for
tallness and
shortness in the F1
plants segregated
from each other
during the formation
of the sex cells, or
gametes.
Knowledge Check
With which organism did Mendel work?
What is meant by self-pollinating?
What is cross pollination?
Knowledge Check
What are genes?
What are alleles?
What is the principle of dominance?
Knowledge Check
What is meant by segregation?
What are gametes?
When have we discussed gametes before?